for some \(\alpha >0\) . This assumption is also made in [1]}, [2]} and [3]}. We also assume that the eigenfunctions of \(K_\alpha \)  are the Fourier basis functions
\(\psi _1(x)=1,\ \psi _{2i}(x)=\sqrt{2}\cos (2\pi ix),\ \psi _{2i+1}=\sqrt{2}\sin (2\pi ix),\quad i\in \mathbb {N},\) 
